1. Field of the Invention
The invention relates to a pipe joint, including a press fitting and a pipe to be connected thereto.
2. Description of the Prior Art
A generic pipe joint with a fitting that encompasses the smooth ends of pipes is known. The fitting has beaded ends, which hold a sealing ring. The beaded end and a cylindrical area of the fitting adjacent to the beaded end are deformed plastically with the pipe. The sealing ring is simultaneously deformed elastically. These deformations are effected by an exchangeable holding device with articulated jaws, which is connected to an operating device (see, for example, the brochure "Mannesmann Press Fitting GmbH" [Mannesmann Pressfitting GmbH] Edition of August 1994). The sealing function of the joint is achieved by virtue of the fact that, due to the plastic deformation of the beaded end, the sealing ring is elastically deformed and, over a certain part of the cross-sectional periphery, comes to rest in line contact on the surrounding surfaces of the beaded fitting and pipe ends. To absorb the longitudinal forces occurring at the existing internal pressure, the cylindrical area of the fitting adjacent to the beaded end is plastically deformed together with the pipe. During pressing, the beaded end and the adjacent cylindrical area are deformed simultaneously by means of the operating device. It is noted on Pages 13 and 14 of the brochure that a correct insertion length for the pipe is essential to a reliable press connection. Here, the "correct insertion length" means that before pressing, the pipe, while being turned slightly and simultaneously pressed in the axial direction, should be inserted up to a stop created by the flange-like depression of a press fitting. A marking previously applied to the pipe serves as a control. However, at construction sites, for reasons of practical work sequence, pipe-laying is not always performed by one completing one section at a time in a step-by step-manner, i.e., measurement, cutting, trimming, insertion and pressing. Instead, several pipe sections to be connected are measured cut and inserted together at the same time. After the several pipe sections are inserted together, then all of the connection points are pressed. Under these circumstances, imprecise measurements of pipe insertion cannot be ruled out, especially in cramped space conditions. It is also possible that a pipe section may be too short to be fully inserted into one or even two press fittings or that an already inserted pipe can withdraw by some amount from a press fitting after alignment of the conduit before the pressing step. Because this withdrawal or displacement cannot be recognized from the outside, pressing is carried out nonetheless. Depending on the degree of withdrawal or displacement, such incorrect pressing points can lead, due to movement of the conduit, to loss of tightness or even, in some cases, to a detached connection.